Testing signal systems



June 24, 1930. c. A. CAMPBELL 1,766,280

TESTING SIGNAL SYSTEMS}.

Filed Feb. 27, 1928 J4 9 J3 J5 18 7 6 7 J9 Qwmwntoz Cfia/z/Yw 51/ ca/mrsbew/ ai bum r Patented June 24, 1930 warren stares PATENT orrica CHARLES A. CAMPBELL, OF WATERTOWN, NEW YORK, ASSIGNOR TO THE NEW YORK AIR BRAKE COMPANY, A. CORPORATION OF NEW JERSEY TESTING SIGNAL SYSTEMS Application filed. February 27, 1928.

This invention relates to signal test de vices, and particularly to such devices for the purpose of checking the condition of the pneumatic whistle signal systems used on railway locomotives and other equipment to enable the conductor or brakeman to signal the engineer.

Such systems include a train pipe, known as the signal pipe, normally charged through a reducing valve from the main reservoir of the air brake system; one or more discharge valves on the various cars, operable to produce local brief reductions of pressure in the signal pipe; a whistle in the engine cab; and a whistle valve mechanism interposed between the signal pipe and the whistle, and responsive to pressure reductions in the signal pipe to cause the whistle to blow once for each such reduction. Devices of this charac- V ter are standard on American railroads.

The whistle valve mechanisms in current use are subject to occasional derangement and before an engine leaves a round house to enter road service, its signal valve must be tested for operativeness. The volume and length of the train signal pipe enter as modifying factors in the functioning of such valves, but nevertheless the test must be made on a locomotive disconnected from a train. There has long been a demand for a convenient and reliable device for making such a test on a locomotive, but prior to the present invention the only devices available so far as known have required a precision of manipulation diflicult to attain, such as timing to a fraction of a second the flow through a restricted orifice.

According to the present invention the signal pipe in charged condition is connected with an uncharged chamber of such volume that the resulting reduction of signal pipe pressure will cause the signal valve to function and blow the whistle. The volume of the chamber is such that the pressure reduction secured is little more than sufficient to Serial No. 257,450.

cause the valve so to function. In testing, the chamber is connected alternately to atmosphere and to the signal pipe and the test consists in producing at least a chosen minimum number of whistle blasts in a chosen time interval, say five or more blasts in ten seconds. i

With a relatively long over-all time interval the need for precision in timing is avoided, and the requirement that the valve function a number of times irnsuccession, checks operation at progressively depleted signal pipe pressures, and checks against interference occasioned by the opening of the feed valve.

The'preferred embodiment of the invention is illustrated in the accompanying drawing, in which Fig. l is a vertical axial section of the test apparatus.

Fig. 2 is an elevation looking to the left relatively to Fig. 1.

Fig. 3 is a fragmentary View of the cock showing it in position'to vent the chamber. Fig. 4 is a similar view showing the cock in position to connect the chamber with the signal pipe and close the vent.

The chamber is composed of a short length of. pipe 6 closed at its ends by caps 7 Threaded into one end cap 7 is a nipple 8 connected by a union 9 to one port 11 of a threeway cock 12. The two other ports are, respectively, 18, which is open to atmosphere, and, 14, which is connected by union 15 and a choked nipple 16 with the interior of annular boss 17 in the face of dummy coupling 18. The dummy coupling 18 has lugs 19 and 21 which mate in a familiar manner with companion lugs on any standard signal pipe hose coupling (not shown) at which time boss 17 seals against the usual coupling gasket. v

The rotary plug 22 of cock 12 is turned by handle 23 and has a 90 range of movement between the positions shown inFigs.

3 and 4;. The'plug 22 has a diametric port- 24 and a radial port 25 at right angles thereto and both in plane with the ports 11, 13 and 14.

In the position of Fig. 3 the plug 22 blanks port 14 (sealing the end of the signal pipe) and ports 11, 25, 24:, 13 then vent the chamber to atmosphere. In the position of Fig. 4 the plug 22 blanks port 13 and ports 14, 24, and 11 connect the signal pipe to the chamber. I

To make a test, coupling 18 is connected to the signal hose coupling at the rear of the tender with cock 22 in the position of Fig. 3. The cut out cock on the signal line is opened. The operator assures himself that the signal pipe is fully charged, and then shifts the handle 23 alternately to its lim-' iting positions as rapidly as'possible, consonant with the attainment of the following two requirements: (1) that the signal Whistle shall blow each time the chamber is connected with the signal pipe, and (2) that the venting flow from the chamber shall substantially cease before the valve is shifted away from chamber venting position. This operation is continued for a definite time period. The system is operative if the Whistle can thus be caused to sound at least a chosen minimum number of times in such time interval.

As an example of a commercial application of the invention, and without intent to limit the invention to the particular details described: ifa chamber of 9.5 cubic inches capacitybe used with a threeway valve having its reduction port in diameter and exhaust port in diameter, a satisfactorily operative brake valve will be indicated by ability to cause five or more blasts of the signal whistle in tenseconds. This test is more or less empirical and applies to the general run of locomotives now encountered. The timing is affected by the size of the chamber and size of the ports, and in some degree by the length of the signal pipe on the locomotive, but experience has shown that a single chamber and valve can be designed to give a standard and truly indicative test despite variations in the lengths of tenders and consequent variations in signal pipe volume.

lVhat is claimed is,-

'1. The method of testing a pneumatic signal system including a signal pipe, signal valve and whistle, which consists in charging thepipe and valve With air; re-

ducing the pressure in said pipe by discharging air therefrom into a chamber of fixed capacity and at a definite lower initial pressure until the pressures in the pipe and chamber equalize; repeating said pressure reducing step'by discharging a1r from said 'pipe successively into confined equal vol umes of air at said definite initial pressure as rapidly as is possible and yet cause the signal valve to function to blow the whistle upon each pressure reduction; and observing the attained number of blasts per unit of time.

2. The method of testing a pneumatic signal whistle system including a signal pipe, signal valve and whistle, which con sists in charging the pipe and valve with air; reducing the pressures in said pipe by discharging air therefrom into a chamber of fixed capacity until the pressures in the pipe and chamber are equalized; then cl0sing communication between the pipe and chamber and venting the chamber to the atmosphere, whereby the pressure in the chamber drops to that of the atmosphere; repeating said pressure-reducing and chamber-venting steps as' rapidly as is possible and yet cause the signal valve to function to blow the whistle upon each pressure reduction; and observing the attained number of blasts per unit of time.

In testimony whereof 'I have signed my name to this specification.

CHARLES A. CAMPBELL. 

